Tool holder with spring operated nut

ABSTRACT

A tool holder assembly includes a hollow supporting member on which there is threaded a locking ring which is urged to its locked position by a pair of parallel equal springs, there being a combined latch and release pin wherein the release pin is directly guided in the supporting member for holding the locking ring in the unlocked position, and responsive to the reception of a tool to be automatically released for automatically tightening the locking ring. The locking springs are disposed in groove means defined by structure which is comovable with the locking ring, the groove being radially outwardly and axially substantially open, and closed by an annular cover of L-shaped cross section telescopically received on the locking ring. The locking ring has a cylindrical flange with a cutout portion defining angularly spaced abutments that engage a stop on the supporting member against which the parallel springs act.

United States Patent 1191 Primary Examiner-Donald R. Schran Assista nt Examiner-W. R. Briggs Attorney, Agent, or FirmHill, Gross, Simpson, Van Santen, Steadman, Chiara & Simpson Koch [45] Aug. 13, 1974 TOOL HOLDER WITH SPRING OPERATED [57] ABSCT NUT A tool holder assembly includes a hollow supporting [75] Inventor: Roland G, Koch, Frank uth, member on which there is threaded a locking ring Mi h, I which is urged to its locked position by a pair of paral- 1 lel equal springs, there being a combined latch and re- [73] Asslgnee' gw Indusmes Buffalo lease pin wherein the release pin is directly guided in the supporting member for holding the locking ring in [22] Filed; May 2, 1972 the unlocked position, and responsive to the reception of a tool to be automatically released for automati- [21] Appl' 249722 cally tightening the locking ring. The locking springs are disposed in groove means defined by structure 52 us. 01. 279/91, 279/1 B which is comovable with the locking ring, the groove 51 1111. c1. B23b 31/06 being radially outwardly and axially substantially [58] Field 61 Search 279/89, 90, 91, 100, 101, Open, and closed by an annular Cover of p 279/97 1 A 1 B 9 R cross section telescopically received on the locking ring. The locking ring has a cylindrical flange with a -[56] References Cit d cutout portion defining angularly spaced abutments UNITED STATES PATENTS that engage a stop on the supporting member against 2,960,243 I 11/1960 1 Elledge 279/1 whlch theparanel Sprmgs 3,512,793 5/1970 Botimer .Q. 279/91 3,663,028 5/1972 King et al. 279/91 PAIENIEU AUG 1 31914 m llllglw TOOL HOLDER WITH SPRING OPERATED NUT I BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to a tool holder and more specifically to a tool holder that automatically locks onto a tool adapter in response to insertion of such adapter in the holder.

2. Prior Art A tool holder having a hollow supporting member and a locking ring threaded thereon for movement between angular limits defined by a pair of pins is shown in U.S. Pat. No. 2,719,722, which is owned by the assignee of the present invention.

A modification of the structure of US. Pat. No. 2,719,722 is shown in U.S. Pat. No. 3,512,793 wherein a latch mechanism has been provided by two separately movable pins respectively biased by separate springs, and respectively retained in the supporting member by separate threaded plugs.

SUMMARY OF THE INVENTION According to this invention, a tool holder assembly includes a hollow supporting member provided with a spring-operated nut under the control of a latch mechanism. The latch mechanism includes a release pin which is directly carried by the supporting member and moves along its own length, parallel to the rotational 2 tion of a tool when the locking ring has been moved beyond the locked position without a tool therein.

Yet another object of the present invention is to provide a safety-type of recess in the locking ring that enables the use of a wrench thereon without providing any projecting structure that could comprise a safety risk.

Many other advantages, features and additional objects of the present invention will become manifest to those versed in the art upon making reference to the detailed description and the accompanying drawings in which a preferred structural embodiment incorporating the principles of the present invention is shown by way of illustrative example.

1 ON THE DRAWINGS:

FIG. 1 is a fragmentary vertical cross-sectional view of a tool holder assembly provided in accordance with the principles of the present invention;

FIG. 2 is a cross sectional view taken along line ll-ll of FIG. 1;

FIG. 3 is a bottom end view of the structure of FIG.

axis, .a latch pin being secured to the release pin with a rigid connection therebetween, the latch pin being movable parallel to the rotational axis, perpendicular to its own length to hold the spring-operated nut or locking ring in the unlocked position. The locking ring has an angular cut-out into which a stop extends, an annular cover of L-shaped radial cross section closing such cut-out to provide a substantially closed groove in which there is disposed two equal parallel helical springs. The locking ring further has a cylindrical flange, a portion of which is removed to define angularly spaced abutments that coact with the stop against which the locking springs act. 1

Accordingly, it is an object of the present invention to provide a tool holder having a spring-operated nut.

A further object of the present invention is to provide in the environment set forth a simple latch mechanism for such nut.

A further object of the present invention is to provide a tool holder assembly having a nut of such configuration as to eliminate the need for relatively costly trepanning during manufacture.

A further object of the present invention is to so construct lock spring means as to reduce manufacturing cost and also so as to reduce reaction time.

A further object of the present invention is to so construct the lock spring means as to enable an increase in manufacturing tolerances that can be given to cooperating parts.

Yet another object of the present invention is to provide a stop and an abutment which engage at the locked position of the locking ring, thereby protecting the latch mechanism against damage.

A still further object of the present invention is to provide a stop and abutment which engage so as to insure a suitable preload on the lock spring means, and also so as to prevent excessive turning of the lock ring, excessive turning being that which would permit recep- FIG. 4 is an elevational view of a tool or tool adapter which can be received in the tool holder assembly of FIG. 1.

AS SHOWN ON THE DRAWINGS:

The principles of the present invention are particu-' larly useful when embodied in a tool holder assembly such as illustrated in FIG. 1, generally indicated by the numeral 10. The tool holder assembly 10 includes a hollow supporting member 11 which has a recess that includes a tapered portion 12 and an outer cylindrical portion 13 which is slotted as at 14 and 15, the end portion of the supporting member 11 being threaded at 16. Adjacent to the threads 16, the supporting member 11 is provided with a radially projecting stop 17 which is threaded securely thereon.

.Conventional structure is provided by which a tool 18 (FIG. 4), the supporting member 11 and a locking ring 19 are secured together for corotation. An example of such structure is shown in US. Pat. No. 2,719,722. With such representative structure, the tool 18 includes an adapter that has a tapered body 20, a cylindrical portion 21, and a pair of ears 22,22. The tapered body 20 is received in the recess 12, the cylindrical portion 21 is received in the recess portion 13, and the ears 22,22 are received in the slots 14,15. The locking ring 19 has threads which mate with the thread 16 on the supporting member 11 and has a flange 23 which has an upper surface 24 that acts on the lower side of the cars 22, 22, the ears being receptive through the flange 23 through a pair of beveled slots 25,25. When the slots 25,25 are aligned with the slots 14,15, the tool 18 can be inserted or withdrawn. Such position of alignment is referred to herein as the locked position of the locking ring 19 which is the position where the tool 18 is not locked and which position is maintained by the latch mechanism described below. Thus the unlocked position of the locking ring 19 is one wherein the tool 18 is locked into the assembly 10. The locking ring 19 has an axially opening notch 26. The locking ring 19 is further provided with groove means 27, and the structure that defines the groove means 27 is all comovable with the locking ring 19 during rotation thereof on its threads 16. The groove means 27 have been provided in such a way as to avoid the necessity of any trepanning operation, and to that'end there is a groove or cutout 28 on the locking ring 19 which opens radially outwardly and which also is axially open. The portion 28 of the groove 27 that is defined by the locking ring 19 thus defines two walls of a substantially enclosed groove which encircles the rotational axis. The other two walls of the substantially closed groove means 27 are provided by an annular cover 29 which has an L-shaped radial cross section and which is telescopically received on the ring 19. The locking ring 19 further has a set of four axially elongated wrenching recesses 30,30 each having the shape of a Woodruff key. This structure is advantageous in that no projection is provided on the outside of the locking ring 19 and thus any threat to an unsafe condition is avoided.

The provision of the groove portion 28 in the locking ring 19 leaves a circumferential flange 31, and as shown in FIG. 2, the flange 31 is cut away for a little more than vl2 degrees at 32 to define a pair of abutments 33,34 that are angularly spaced from one another. The stop 17 projects horizontally between the abutments 33,34 and so the coaction between the abutment 33 and the stop 17 limits the amount that the locking ring 19 can be loosened or unscrewed, and also serves to define accurately the position of slot alignment shown in FIG. 1 and described previously. The coaction between the abutment 34 and the stop 17 limits the amount that the locking ring 19 can be tightened. When there is a tool 18 in the recess 12, the tool actually limits the amount that the locking ring 19 can be tightened, but in the absence of such a tool, where it not for the cooperation between the abutment 34 and the stop 17, the locking ring 19 could be rotated in a tightening direction for 180 degrees from the position illustrated so as to create a slot alignment which would be spurious.

In the groove means 27, there is provided lock spring means 35. In this embodiment, the lock spring means 35 comprises two equal helical coil springs 36,36 of the compressiontype disposed in parallel to each other in the groove means 27. One end of the springs 36,36 acts against a dowel pin 37 secured to the locking ring 19, and the other ends of the springs 36,36 each receive a pilot 38 carried on a block 39 that also acts against one side of the stop 17. This arrangement of lock spring means is particularly advantageous. Previously, to get the necessary spring force, a pair of concentric springs were provided which inherently and necessarily had different parameters, and one of these differences was in the total number of coils. With such an arrangement, the coils of one spring tended to rub against the other so as to produce a rather slow reaction time. With the present arrangement, reaction time is shortened and procurement cost is reduced since only one type of part is needed. Further, with this arrangement, a greater rotation of the locking ring is possible before the spring reaches its solid height, and therefore the angular spacing between the abutments 33,34 has thus been able to be increased by 30 degrees, thereby enabling use of less exacting tolerances in related parts, such as in the thickness of the ears 22,22 on the tool 18.

The latch mechanism by which the locking ring 19 is held in its locked position (tool unlocked position) includes a release pin 40 which is directly slidably carried by the supporting member 11 and which moves along its own length, parallel to the rotational axis of the toolholder assembly. A spring 41 acting between the supporting member 11 and the release pin directly urges the release pin toward the tool, and for that reason, the release pin 40 tends to or normally projects from the end of the supporting member 11 into the slot 14. When one of the ears 22 of the tool 18 engages the lower end of the release pin 40, the release pin 40 is thus forced by the tool 18 against the force of the spring 41 to a retracted position. A latch pin 42 has a rigid connection with the release pin 40, and the pins 40, 41 project transversely to each other. The latch pin 42 is thus moved by the release pin 40 in a direction which is perpendicular to its own length and which is parallel to the rotational axis. When the tool 18 is removed, the spring 41 through the release pin 40 thus urges the latch pin 42 to enter the notch 26 in the flange 31 of the locking ring 19. A slot 43 in the wall the supporting member 11 enables such vertical movement of the pins 42, the slot 43 being vertically elongated.

In operation, the structure of FIG. 4 is inserted into the structure of FIG. 1 and one of the ears 22 shifts the release pin 40 upwardly, thereby also raising the latch pin 42 until it clears the vertical edge of the notch 26, whereupon the lock spring means 35 rotates the locking ring 19 to clamp the tool firmly in position for corotation. When the locking ring 19 is rotated with respect to the supporting member 11, such rotation continues until the slots 25 are aligned with the ears 22 whereupon the tool 18 becomes released and moves downwardly by gravity, andwhenever the slots 14,15 are so aligned with the slots 25, the notch 26 is aligned with the latch pin 42 so that it can drop into such notch. In the event that the locking ring 19 is rotated rapidly to achieve such alignment, the latch pin 42 is protected against damage by virtue of the simultaneous engagement of the abutment 33 with the stop 17. In the event that the release pin 40 is actuated by some other instrumentality, the lock ring 19 is restricted by the abutment 34 and the stop 17 to provide less than one-half turn of movement, such engagement also serving to preserve the preload on the lock spring means 35.

Although various minor modifications might be suggested by those versed in the art, it should be understood that I wish to embody within the scope of the pa tent warranted hereon, all such embodiments as reasonably and properly come within the scope of my contribution to the art.

I claim as my invention:

1. A tool holder assembly comprising:

a. a hollow supporting member adapted to be secured to a machine tool spindle, having a recess for receiving a tool, and having a threaded end portion;

b. a tool having a portion to be received in said recess;

c. a threaded locking ring carried on said threaded end portion;

d. means on said supporting member, on said tool and on said locking ring to lock said tool onto said supporting member for driven corotation, said locking ring being movable to a locked and an unlocked position;

e. lock spring means acting between said supporting member and said locking ring and urging said locking ring to move to the locked position;

f. a release pin directly slidably carried by said supporting memberfor movement along its length in a direction parallel to the rotational axis of the supporting member, and normally projecting from said supporting member into a portion of said recess to be engaged by the tool as the tool is received in said supporting member;

g. a spring directly urging said release pin toward said tool; and

h. a latch pin having a rigid connection with said release pin and projecting radially therefrom through an axially elongated radially open slot in said supporting member, said latch pin being movable in a direction perpendicular to its length into an axially opening notch in said locking ring.

2. A tool holder assembly according to claim 1 which includes means comovable with said locking ring defining a substantially enclosed groove encircling the rotational axis in which said lock spring means is disposed.

3. A tool holder assembly according to claim 2 in which said groove means comprises a radially outwardly as well as axially open groove in said locking ring, and an annular cover of L-shaped cross section telescopically received on said locking ring and substantially closing said groove.

4. A tool holder assembly according to claim 1 in which said lock spring means comprises two equal springs disposed in parallel to each other.

5. A tool holder assembly according to claim 1 in which said locking ring has a set of radially outwardly opening axially elongated recesses, each of the recesses having the shape of a Woodruff key.

6. A tool holder assembly according to claim 1 including a radially projecting stop on said supporting member, and a movable pair of angularly spaced abutments on said locking ring, one of said abutments being engageable with one side of said stop at said unlocked position, and the other of said abutments being engageable with the other side of said stop to limit the rotation of said locking ring in absence of said tool.

7. A tool holder assembly according to claim 6 in which said locking ring has a cylindrically shaped f. means rigidly secured to and comovable with said locking ring defining a substantially enclosed groove encircling the rotational axis in which said lock spring means is disposed, said groove means comprising a radially outwardly as well as axially open groove in said locking ring, and an annular cover of L-shaped cross section telescopically rigidly corotatably received on said locking ring and substantially closing said groove;

g. a latch pin movable in a direction parallel to the rotational axis of said locking ring into a position where it holds said locking ring in the unlocked position;

h. a release pin having a rigid connection with said latch pin and projecting transversely therefrom such that it can be engaged by the tool as the tool is received by the tool holder;

i. only one of said pins being directly slidably carried by said supporting member for movement along its length in a direction parallel to the rotational axis of the supporting member; and

j. a spring urging said one pin toward said tool.

10. A tool holder assembly according to claim 9 in which said lock spring means comprises two equal springs disposed in parallel to each other.

11. A tool holder assembly according to claim 9 including a single radially projecting stop on said supporting member, and a pair of angularly spaced abutments on said locking ring, one of said abutments being engageable with one side of said stop'at said unlocked position, and the other of said abutments being engageable with the other side of said stop to limit the rotation flange with a cut-out portion defining said abutments. 4

8. A tool holder assembly according to claim 1 including a stop on said supporting member, and a pair of angularly spaced abutments on said locking ring engageable with said stop, one of said abutments providing a preload on said lock spring means. 9. A tool holder assembly comprising: a. a hollow supporting member adapted to be secured to a machine tool spindle, having a recess for receiving a tool, and having a threaded end portion;

of saidlocking ring in absence of said tool.

12. A tool holder assembly according to claim 11 in which said locking ring has a cylindrically shaped flange with a cut-out portion defining said abutments.

13. A tool holder assembly according to claim 9 including a single stop on said supporting member, and a pair of angularly spaced abutments on said locking ring engageable with said stop, one of said abutments providing a preload on said lock spring means.

14. A tool holder assembly comprising:

a. a hollow supporting member adapted to be secured to a machine tool spindle, having a recess for receiving a tool, and having a threaded end portion;

b. a tool having a portion to be received in said recess;

c. a threaded locking ring carried on said threaded end portion;

d. means on said supporting member, on said tool and on said locking ring to lock said tool onto said supporting member for driven corotation, said locking ring being movable to a tool locked and unlocked position;

e. lock spring means acting between said supporting member and said locking ring and urging said lockingring to move to the locked position, said lock spring means comprising two equal helical coil springs disposed in parallel to each other;

f. a block having two pilots projecting into the endmost coil of said springs and acting against said supporting member;

g. a latch pin movable in a directional parallel to the rotational axis of said locking ring into a position where it holds said locking ring in the unlocked position;

of the supporting member; and j. a spring urging said one pin toward said tool.

15. A tool holder assembly according to claim 14 including a single radially projecting stop on said supporting member, and a pair of anguarly spaced abutments on said locking ring, one of said abutments being engageable with one side of said stop at said unlocked position, and the other of said abutments being engageable with the other side of said stop to limit the rotation of said locking ring in absence of said tool.

16. A tool holder assembly according to claim 15 in which said locking ring has a cylindrically shaped flange with a cut-out portion defining said abutments.

17. A tool holder assembly according to claim 14 including a single stop on said supporting member, and a pair of angularly spaced abutments on said locking ring engageable with said stop, one of said abutments providing a preload on said lock spring means.

18. A tool holder assembly according to claim 14 in which said equal springs are helical coil springs, and a block having two pilots projecting into the endmost coils of said springs and acting against said stop.

19. A tool holder assembly comprising:

a. a hollow supporting member adapted to be secured to a machine tool spindle, having a recess for receiving a tool, having a threaded end portion, and

having a single radially projecting stop secured thereto;

b. a tool having a portion to be received in said recess;

c. a threaded locking ring carried on said threaded end portion, said locking ring being movable to a tool-locked and an unlocked position, said locking ring having a cylindrically shaped flange with a cutout portion defining a movable pair of angularly spaced abutments fixed thereon for respectively engaging oppositely directed surfaces on said stop at said locked position and to limit rotation of said locking ring in absence of said tool;

(1. means on said supporting member, on said tool and on said locking ring to lock said tool onto said supporting member for driven corotation;

e. lock spring means acting between said supporting member on said locking ring and urging said locking ring to move to the locked position;

f. a latch pin movable in a direction parallel to the rotational axis of said locking ring into a position where it holds said locking ring in the unlocked position;

g. a release pin having a rigid connection with said latch pin and projecting transversely therefrom such that it can be engaged by the tool as the tool is received by the tool holder;

h. only one of said pins being directly slidably carried by said supporting member for movement along its length in a direction parallel to the rotational axis of the supporting member; and

i. a spring urging said one pin toward said tool. 

1. A tool holder assembly comprising: a. a hollow supporting member adapted to be secured to a machine tool spindle, having a recess for receiving a tool, and having a threaded end portion; b. a tool having a portion to be received in said recess; c. a threaded locking ring carried on said threaded end portion; d. means on said supporting member, on said tool and on said locking ring to lock said tool onto said supporting member for driven corotation, said locking ring being movable to a locked and an unlocked position; e. lock spring means acting between said supporting member and said locking ring and urging said locking ring to move to the locked position; f. a release pin directly slidably carried by said supporting member for movement along its length in a direction parallel to the rotational axis of the supporting member, and normally projecting from said supporting member into a portion of said recess to be engaged by the tool as the tool is received in said supporting member; g. a spring directly urging said release pin toward said tool; and h. a latch pin having a rigid connection with said release pin and projecting radially therefrom through an axially elongated radially open slot in said supporting member, said latch pin being movable in a direction perpendicular to its length into an axially opening notch in said locking ring.
 2. A tool holder assembly according to claim 1 which includes means comovable with said locking ring defining a substantially enclosed groove encircling the rotational axis in which said lock spring means is disposed.
 3. A tool holder assembly according to claim 2 in which said groove means comprises a radially outwardly as well as axially open groove in said locking ring, and an annular cover of L-shaped cross section telescopically received on said locking ring and substantially closing said groove.
 4. A tool holder assembly according to claim 1 in which said lock spring means comprises two equal springs disposed in parAllel to each other.
 5. A tool holder assembly according to claim 1 in which said locking ring has a set of radially outwardly opening axially elongated recesses, each of the recesses having the shape of a Woodruff key.
 6. A tool holder assembly according to claim 1 including a radially projecting stop on said supporting member, and a movable pair of angularly spaced abutments on said locking ring, one of said abutments being engageable with one side of said stop at said unlocked position, and the other of said abutments being engageable with the other side of said stop to limit the rotation of said locking ring in absence of said tool.
 7. A tool holder assembly according to claim 6 in which said locking ring has a cylindrically shaped flange with a cut-out portion defining said abutments.
 8. A tool holder assembly according to claim 1 including a stop on said supporting member, and a pair of angularly spaced abutments on said locking ring engageable with said stop, one of said abutments providing a preload on said lock spring means.
 9. A tool holder assembly comprising: a. a hollow supporting member adapted to be secured to a machine tool spindle, having a recess for receiving a tool, and having a threaded end portion; b. a tool having a portion to be received in said recess; c. a threaded locking ring carried on said threaded end portion; d. means on said supporting member, on said tool and on said locking ring to lock said tool onto said supporting member for driven corotation, said locking ring being movable to a tool-locked and an unlocked position; e. locking spring means acting between said supporting member and said locking ring and urging said locking ring to move to the locked position; f. means rigidly secured to and comovable with said locking ring defining a substantially enclosed groove encircling the rotational axis in which said lock spring means is disposed, said groove means comprising a radially outwardly as well as axially open groove in said locking ring, and an annular cover of L-shaped cross section telescopically rigidly corotatably received on said locking ring and substantially closing said groove; g. a latch pin movable in a direction parallel to the rotational axis of said locking ring into a position where it holds said locking ring in the unlocked position; h. a release pin having a rigid connection with said latch pin and projecting transversely therefrom such that it can be engaged by the tool as the tool is received by the tool holder; i. only one of said pins being directly slidably carried by said supporting member for movement along its length in a direction parallel to the rotational axis of the supporting member; and j. a spring urging said one pin toward said tool.
 10. A tool holder assembly according to claim 9 in which said lock spring means comprises two equal springs disposed in parallel to each other.
 11. A tool holder assembly according to claim 9 including a single radially projecting stop on said supporting member, and a pair of angularly spaced abutments on said locking ring, one of said abutments being engageable with one side of said stop at said unlocked position, and the other of said abutments being engageable with the other side of said stop to limit the rotation of said locking ring in absence of said tool.
 12. A tool holder assembly according to claim 11 in which said locking ring has a cylindrically shaped flange with a cut-out portion defining said abutments.
 13. A tool holder assembly according to claim 9 including a single stop on said supporting member, and a pair of angularly spaced abutments on said locking ring engageable with said stop, one of said abutments providing a preload on said lock spring means.
 14. A tool holder assembly comprising: a. a hollow supporting member adapted to be secured to a machine tool spindle, having a recess for receiving a tool, and having a threaded end portion; b. a tool havIng a portion to be received in said recess; c. a threaded locking ring carried on said threaded end portion; d. means on said supporting member, on said tool and on said locking ring to lock said tool onto said supporting member for driven corotation, said locking ring being movable to a tool locked and unlocked position; e. lock spring means acting between said supporting member and said locking ring and urging said locking ring to move to the locked position, said lock spring means comprising two equal helical coil springs disposed in parallel to each other; f. a block having two pilots projecting into the endmost coil of said springs and acting against said supporting member; g. a latch pin movable in a directional parallel to the rotational axis of said locking ring into a position where it holds said locking ring in the unlocked position; h. a release pin having a rigid connection with said latch pin and projecting transversely therefrom such that it can be engaged by the tool as the tool is received by the tool holder; i. only one of said pins being directly slidably carried by said supporting member for movement along its length in a direction parallel to the rotational axis of the supporting member; and j. a spring urging said one pin toward said tool.
 15. A tool holder assembly according to claim 14 including a single radially projecting stop on said supporting member, and a pair of anguarly spaced abutments on said locking ring, one of said abutments being engageable with one side of said stop at said unlocked position, and the other of said abutments being engageable with the other side of said stop to limit the rotation of said locking ring in absence of said tool.
 16. A tool holder assembly according to claim 15 in which said locking ring has a cylindrically shaped flange with a cut-out portion defining said abutments.
 17. A tool holder assembly according to claim 14 including a single stop on said supporting member, and a pair of angularly spaced abutments on said locking ring engageable with said stop, one of said abutments providing a preload on said lock spring means.
 18. A tool holder assembly according to claim 14 in which said equal springs are helical coil springs, and a block having two pilots projecting into the endmost coils of said springs and acting against said stop.
 19. A tool holder assembly comprising: a. a hollow supporting member adapted to be secured to a machine tool spindle, having a recess for receiving a tool, having a threaded end portion, and having a single radially projecting stop secured thereto; b. a tool having a portion to be received in said recess; c. a threaded locking ring carried on said threaded end portion, said locking ring being movable to a tool-locked and an unlocked position, said locking ring having a cylindrically shaped flange with a cut-out portion defining a movable pair of angularly spaced abutments fixed thereon for respectively engaging oppositely directed surfaces on said stop at said locked position and to limit rotation of said locking ring in absence of said tool; d. means on said supporting member, on said tool and on said locking ring to lock said tool onto said supporting member for driven corotation; e. lock spring means acting between said supporting member on said locking ring and urging said locking ring to move to the locked position; f. a latch pin movable in a direction parallel to the rotational axis of said locking ring into a position where it holds said locking ring in the unlocked position; g. a release pin having a rigid connection with said latch pin and projecting transversely therefrom such that it can be engaged by the tool as the tool is received by the tool holder; h. only one of said pins being directly slidably carried by said supporting member for movement along its length in a direction parallel to the rotational axis of the supporting member; and i. a spring urging said one pin toward saiD tool. 